Because the local access telephone market is being deregulated, there is a need for the incumbent monopoly telephone service provider (the local phone company) to unbundle services and resources to make them available to competitive access providers. One area of such unbundling that is particularly complicated occurs when the consumer is served from a remote terminal (e.g., subscriber loop carrier), instead of a direct copper-wire pair. Subscriber loop carriers (SLCs) provide primary connection of the subscriber telephone to the public switched telephone network (PSTN) for clusters of subscribers. There are many thousands of SLCs used in both the United States and internationally. These SLCs are commonly used to provide telephone service in rural and suburban communities where direct connection to the telephone switching office for each individual subscriber would require a large number of long wire pairs, amplifiers, etc., but are also becoming more common in urban areas. In fact, many incumbent monopoly telephone service providers are using SLCs to reduce the cost of physical maintenance of the outside plant.
FIG. 1 illustrates a typical prior art SLC 100. SLC 100 is connected to a plurality of subscribers, herein illustrated as houses 102, 104, and 106 in a suburban or rural community via lines 108-112 respectively. SLCs are also used in urban areas, as mentioned above, such as high height and high density housing units.
SLC 100 comprises a central office portion 114 and a field or remote portion 116. The remote portion 116 of SLC 100 is housed on a pedestal or enclosure in proximity to the subscribers which it serves. The subscriber lines (copper pair or "tip and ring", as is known in the art) are connected to the remote portion 116 of SLC 100 at a plurality of line cards 118, as known in the art. The SLC line cards 118 are generally similar to line cards found in any prior art switching system and provide the BORSHT functionality of telephone service (battery, over voltage, ringing, supervision, hybrid, and testing, as is known in the art). These line cards are plugged into an optical network unit (ONU) 120, which receives and transmits signals to and from the line card, performs translations and prepares the signals for transmission to the central office 114. ONU 120 is controlled by control unit 122. A host digital terminal 124 at central office 114 is connected to the optical network via a plurality of facilities 128-132, which carry multiplexed signals from line cards 118, on 24 channels each (such facilities are commonly DS 1). Host digital terminal 124 is generally located at the switch portion 114 and is connected to a host switch 134. Host digital terminal 124 emulates copper pair appearance at the switch site and terminates the trunks on a special integration unit to the telephone switching system 134. Host switch 134 then can connect calls between SLC 100 and the public switch telephone network (PSTN) 136. SLC 100 may be a SLC 96.RTM. as available from AT&T and described in Bell Laboratories Technical Journal, vol. 63, No. 10, Part 2, December, 1984. In some instances, the host digital terminal is fully integrated into a switch. It is illustrated here as being separate for clarity.
In most arrangements, there is a dedicated control channel 138 between host digital terminal 124 and control unit 122 of optical network 120. This control channel 138 is used to provide supervision, set up phone calls, etc., as is known in the art and described in the above reference. A test bus 142 is also provided between the host switch 134 and host digital terminal 124, and between host digital terminal 124 and remote terminal 116. Test bus 142 is used by craft at host switch 134 (or via a remote link to host switch 134, not shown but well known in the art) to test host digital terminal 124, and remote terminal 116 and lines, such as 108-112. Test bus 142 may be "looped back" at host digital terminal 124 and remote terminal 116 to provide test configuration actions for fault localization, as is known in the art.
In order to provide a competitive access provider switch with access to a subscriber loop carrier, there are several resources that must be "unbundled." First, a plurality of voice channels of the facility between the incumbent monopoly switch and the remote terminal must somehow be connected to the competitive access provider switch. Second, the competitive access provider switch 140 must have some access to control channel 138. Finally, there must be test access from the competitive access provider switch to remote terminal 122 for testing voice channels.
Since there are many talk channels (in the DS 1s) these can be easily unbundled and redirected to the competitive access provider switch by physically removing one or more trunks from the host digital terminal 124 and physically attaching them to a similar facility at the competitive access provider switch 140. Furthermore, test access to lines 108-112 can be achieved. using a variety of telemetry arrangements on the market today. Remote terminal 116, however, can only be tested from host switch 134.
Since there is only one control channel 138 and one test bus 142 per remote terminal 116, it is necessary that these facilities be shared with the competitive access provider switch 140. Such sharing is difficult because the control channel 138 is generally integrated into the switching equipment 134 of the monopoly service provider switching system 114, and is not designed for access by other switches. Also, the protocols used to control some remote terminals are proprietary, and only the switches made by a given manufacturer are capable of communicating with the control unit of the remote terminal. Competitive access service cannot be offered without the use of the control channel because it is used to report offhook and onhook conditions, alarms, etc., from the remote terminal for every line.
Therefore, a problem in the art is that there is no way to unbundle the control channel and test facilities from a monopoly telephone service provider so that a competitive access telephone service provider may control selected lines in a remote terminal on a comparably efficient basis.